Tangy with vinegar and sweet with dried currants, the marinade for this fish is called saor in Italian. The dish is ideal as a first course and wonderful as part of the multicourse Christmas Eve feast. Sole may be substituted for flounder, if you prefer.
1-1/2 pounds flounder filets
Kosher or sea salt and freshly ground black pepper, to taste
All-purpose flour for dredging
1 cup plus 1/4 cup olive oil, divided
2 large onions, thinly sliced
1 large clove garlic, minced
3 bay leaves
1 cup white wine vinegar
3/4 cup dry vermouth
1/3 cup dried currants
1/4 cup pine nuts
2 tablespoons sugar
Season fish with salt and pepper; dredge with flour, patting off excess.
In a medium sauté pan, heat 1 cup olive oil over medium-high heat. When oil is shimmering, fry fish until golden on both sides. Transfer fish to a nonreactive serving bowl just large enough to hold it in one layer; set aside.
Discard oil in pan. Add remaining 1/4 cup oil and onions and cook over medium heat until onions are translucent. Add garlic and bay leaves and cook 1 minute. Add vinegar and vermouth, then stir in currants, pine nuts, and sugar and bring to a boil. Reduce heat and simmer 5 minutes. Remove bay leaves and pour marinade over fish. Let cool to room temperature, then cover and refrigerate 24 hours before serving.